Search

Soil organic carbon (OC) levels generally increase with increasing clay and silt content under a similar climatic zone because of increased association of OC to clay minerals and stronger occlusion inside aggregates. Surprisingly though, in Western Europe many silt loam soils actually bear low topsoil OC levels compared to lighter textured soils. Soil texture obviously also strongly controls moisture availability with consequent indirect impact on heterotrophic activity. We hypothesized that with increasingly frequent summer drought: 1) soil microbial activity in sandy soils is more likely impeded due to their limited water holding capacity retention during droughts, while soil OC mineralization in silty soils remain be less drought-limited; 2) capillary rise from sufficiently shallow groundwater would, on the other hand, alleviate the water stress in lighter textures. To test these hypotheses, we established a one-year field trial with manipulation of soil texture, monitoring of soil moisture and maize-C decomposition via 13/12C-CO2 emissions. The upper 0.5 m soil layer was replaced by sand, sandy loam and silt loam soil with low soil OC. Another sandy soil treatment with a gravel layer was also included beneath the sand layer to exclude capillary rise. Soil texture did not affect maize-C mineralization (Cmaize-min) until April 2019 and thereafter Cmaize-min rates were higher in the silt loam than in the sandy soils (P=0.01). θv correlated positively with the Cmaize-min rate for the sand-textured soils only but not for the finer textures. These results clearly highlight that soil texture controlled Cmaize-min indirectly through regulating moisture under the field conditions starting from about May, when soils faced a period of drought. By the end of the experiment, more added Cmaize was mineralized in the silt loam soil (81%) (Pmaize-min in the sandy soil, seemingly because the capillary fringe did not reach the sandy topsoil layer. These results imply that, under future climate scenarios the frequency of drought is expected to increase, the largely unimpeded microbial activity in silty soils might lead to a further stronger difference in soil OC with coarser textured soils under similar management.

There is a wide variety of agricultural waste co- and by-products that could potentially be valorised in high-value applications. One of such products is lignin, the second most abundant organic biopolymer after cellulose. Because of the large amounts of pruning wastes in the Mediterranean regions, lignin extraction can be one of the possibilities for valorisation and sustainable management of agricultural wastes. Research on the application of lignin, particularly lignosulfonates, is limited to its use as a biostimulant for root growth under controlled laboratory conditions and as a complexing agent in micronutrient foliar fertilizer formulations. Little is known about the impacts of lignin extracted from various feedstock on plant growth and soil quality. We investigated the potential of lignin as plant biostimulator and soil conditioner in a pot experiment with fresh soil and lignin extracts obtained from three types of pruning wastes (urban trees, fruit and forest trees) using ryegrass as a test plant, under laboratory conditions. Two doses of lignin extracts (equivalent to 5 and 20 kg lignin-C ha-1) were applied to assess whether the effect on plant growth and soil quality depends on the rate of application. Soil and plant parameters were determined seven weeks after the grass was planted at 17 °C and 16 h photoperiod. Root biomass significantly increased (62-152%) in treatments with lignin addition, particularly lignin from urban and forest pruning wastes compared to the control. However, the increase in root biomass did not result in a simultaneous increase in shoot biomass or N uptake showing the need to apply additional plant nutrient. The microbial biomass C did not significantly respond to the application of lignin. A significantly higher dehydrogenase enzyme activity was recorded in samples with the high dose of lignin extracted from the urban wastes compared to the lower dose. Urban waste lignin extract contains 15-18 times more total N compared to the lignin extracts from forest and fruit trees, which could explain its significant effect on enzymatic activities and root biomass. The findings show that differences in feedstock properties may influence the plant growth stimulating activity of the lignin. Further research is needed to improve the plant growth-stimulating effect of lignin, to investigate the simultaneous application of the major plant nutrients and the response of the microbial community to lignin application.

Diffuse groundwater contamination by intense fertilizer use is a widespread problem in most of the agricultural regions in West-Europe and in many other countries worldwide. As a result elevated nitrate concentrations in groundwater are found, and as groundwater is the source of baseflow into rivers and streams, also surface waters show increased nitrate levels. Flanders in the north of Belgium is no exception and despite restrictions on the fertilizer use and remediation practices initiated in the mid-1990s, and still ongoing, in many stream monitoring points, peak concentrations are measured above the 50 mg/l criterium. In many monitoring stations there is apparently a long delay between the start of the restrictions and effect on water quality. Often this delay is related to high concentrations in the groundwater inflow and long residence and travel times of groundwater feeding the streams. To better understand this behavior and estimate response times a tool was developed that incorporates the main water flows in a typical catchment and considers the effects of varying groundwater ages. This tool is conceived as a parsimonious lumped parameter model, simple and easy enough to be used by many people but still capturing the main mechanisms end processes. In this paper the tool is explained and it is applied on two testcases in Flanders to show its performance.

Despite massive efforts over the past twenty-five years to reduce nitrogen (N) losses, too high nitrate (NO3−) concentrations in surface and groundwater from agricultural sources remain a major environmental concern, especially in field grown vegetable production areas. A strict restriction of the N fertiliser application rates is accepted to be the best N management strategy to minimise NO3− leaching losses to surface and groundwater. We analysed Flemish field experiments on lettuce, spinach, leek, carrots, cauliflower and Brussels sprouts with various N fertiliser application rates (2009–2016) with a view to fine-tune the N fertiliser application rates where possible. To find an economic and ecological optimum we considered both yield quantity, quality (leaf colour and uniformity for all vegetables, and nitrate concentration for leafy vegetables) and residual soil mineral N (RSMN) to rooting depth at harvest in function of crop available N. Even at relatively high crop available N, NO3− concentrations in lettuce and spinach remained below the legal maximum concentration. Contrary to some farmers’ perception, low RSMN can be obtained without a low score for quality parameters leaf colour and uniformity, except for the un- and underfertilised plots. When crop available N exceeds the optimum, RSMN increased steeply (i.e. a breakpoint) for all considered vegetables, except carrots, implying an increased risk of NO3− leaching. The results indicate that N fertilisation advices and maximum allowed N fertiliser application rates can be reduced, at least for some vegetables, without a risk of decreasing the marketable yield quantity and quality. As N uptake continues to increase, to a variable extent, after the maximum marketable yield has been obtained, N fertiliser application rates obviously should be based on marketable yield rather than total yield.

Soil phosphorus (P) leaching is one of the major causes of diffuse P losses towards the environment in north-west Europe. In order to cut back these P losses over the long term, soil P stocks need to be drastically reduced. Greenhouse experiments have shown that a rapid reduction of the plant available P pool is attained by reducing the P fertilizer input to zero while cropping, but field trials confirming these findings are rare. Moreover, important additional questions arise in any P mining strategy: (i) to what extent will crop performance be affected in high P soils under 0 P fertilization, (ii) which crops reduce soil P stocks most efficiently and (iii) how can soil organic carbon (SOC) levels be maintained when organic fertilizers are no longer applied. In order to address these questions we set up two 0 P fertilization field trials at sites with a very high initial soil P status (i.e. a P saturation degree > 30%). On each site, we compared the effect of 0 P fertilization on crop yield, soil P status and SOC level to a business as usual scenario, for two crop rotations. At the first site, a comparison was made between a mixed crop rotation with or without the inclusion of a catch crop. At the second site, a comparison was made between an arable/grass and a vegetable crop rotation. Four consecutive years of 0 P fertilization had no effect on neither the crop yield nor the crop P uptake. Further, English ryegrass, silage maize, celeriac and Chinese cabbage made the largest contribution to P removal. Although 0 P fertilization reduced the P balance at field level with 102–121 kg P ha-1 over four years, this had no significant (measurable) effect yet on the soil P stocks. Continuation of these experiments over a longer time will thus be needed to allow to see any such effects. Simulations of the evolution of the SOC levels over a thirty-year period showed that the use of grass as green manure or as main crop only allows to partially maintain the SOC levels in the absence of any organic fertilizers. These results indicate that P mining is a challenging task, that will take a long time to reduce the soil P stocks and that will come at a cost for the farmer.

Nitrogen (N) depositions in Europe are decreasing, but this could not explain faster than expected improvement of N saturation indicators in temperate forests. Alongside there were local signs of initial recovery from acidification during the past three decades and enhanced leaching of dissolved organic carbon and nitrogen (DOC, DON). These two global change processes both affect total dissolved nitrogen (TDN) levels and often occur simultaneously, hence complicating mechanistic explanations for changing European forest N status. We aimed to test the hypothesis that forest N status in northwest Europe has started to improve. If this hypothesis is confirmed, we wanted to investigate to what extent such improvement is due to reduced N deposition. We evaluated the evolution of multiple N saturation indicators in five ICP Forests Level II plots in northern Belgium, using long-term soil solution and foliage datasets. The DON:TDN ratio (molar) in soil solution increased overall in the O horizon (mean 0.279–0.463, slope 0.023–0.037 yr −1 ) and in the mineral soil (mean 0.134–0.78, slope 0.007–0.051 yr −1 ) between 2005 and 2014. The DOC:NO 3 − ratio (molar) in soil solution increased in three plots in the O horizon (mean 6.84–22.15, slope 0.58–1.92 yr −1 ) and in four plots in the mineral soil (mean 2.07–25.32, slope −0.06–5.76 yr −1 ) between 2002 and 2014. The ratio of N and phosphorus (P) concentrations in foliage (mg g −1 ) and the ratio of base cations (Bc = Ca + K + Mg) and N concentrations in foliage (molar) remained unaltered between 1999 and 2013. Changes in the soil solution chemical composition thus confirmed an improvement in forest N status, despite sustained high NO 3 − concentrations, but biotic recovery appeared to be lagging behind. This demonstrates that insight in forest recovery from N saturation requires a multiple indicator approach, and further monitoring of tree nutritional status alongside soil processes is needed to monitor the evolution of European forest N status.

Long-term field experiments have confirmed belowground plant carbon (C) to be two to three times more efficient precursor of soil organic carbon (SOC) than aboveground plant residues. But it remains elusive just when this belowground biomass is relatively stabilized against mineralization: during the initial fast degradation, or on the longer term? A one-year field experiment was set up with biweekly follow-up of the in-situ mineralization of maize (Zea mays L.) C-inputs, either above- or belowground biomass based on soil δ13C resolved CO2 emissions. In addition, a treatment with maize roots and post-harvest remnant rhizodeposited-C left undisturbed in the field was included as well as a corresponding control that was physically disturbance as in the other treatments. We found that most maize-C was mineralized within a year with peaks in late fall and spring, i.e. 1 and 8 months after incorporation. Shoot-C decomposed only 1.4 times faster than root-C though statistically insignificant, which shows that on the short term (i.e. within a single year) the 2–3 fold stability of belowground biomass C is not manifested. Total maize-derived CO2 emissions of soil amended with only roots and with roots and post-harvest rhizodeposits were equal, likely because the rhizodeposited-C had already degraded quickly. A much smaller share of root- and rhizodeposited-C (43%) was mineralized when soil was not disturbed after harvest. We hypothesize that such a delayed physical disturbance, which in practice would only occur in early spring, could be key in stabilizing belowground biomass C in the field. Overall, our findings show a limited difference in degradability of roots and shoots under field conditions on the short term, and a large effect of tillage timing.

High rainfall intensity is major factor governing leaching process, where leaching is often the most important process of N loss from the field and lead to agricultural environmental pollution. In order to measure the movement of mineral-N in soil profile, a field research had been conducted in two sites of center vegetable farming area with six farmer cooperators in Central Java, Indonesia. Regular soil sampling was done from Improve Practice (IP) and Farmer Practice (FP) treatment for three planting seasons during 2007. Almost all treatments FP applied higher rate of N fertilizer compare to IP, but it was not reflected in N profile. Comparison of predicted and measured mineral N content was simulated using Burns α model, then the closeness of the estimation and measured calculated using Coefficient of Residual Mass (CRM) calculation as an indicator with 0 as ideal value. Out of 9 measurements of IP and FP treatment, eight and seven measurements had negative CRM representinga slight overestimation. The NO3-N loss estimated using the Burns α model for IP and FP was in average of 67% for IP and 71% for FP of total N fertilizer added or 67% for IP and 76% for FP of total-N surplus, respectively. The calculation of potential nitrate concentration (PNC) at 1 m soil depth at the end of the third season showed a high concentration with significant different of IP and FP having mean value of 59.8 and 82.5 mg N L-1. From the gathered data it was obvious that over N fertilization had negative effect to agricultural environment.

The few available studies on maize biomass in soil of field experiments have shown that belowground maize biomass resides more than twice as long as aboveground residues. Our principal objective was to investigate the effect of maize crop residue incorporation on the long-term dynamics of soil organic carbon (SOC) for a selection of croplands with sandy to sandy loam texture in Flanders, Belgium. After a period of more than 20 years, we resampled 31 and 29 parcels that had either silage maize (MS, only belowground biomass input) or grain maize (MG, both above- and belowground biomass input) dominated crop rotations. Changes in maize-derived SOC (Cmaize) of MS and MG systems between 1993 and 2018 were evaluated by detecting SOC content and its δ13C value. In addition, a 140-day incubation experiment (at 20.5 °C) was carried out to compare the stability of Cmaize and the related nitrogen (N) mineralization between the MG and MS fields. After two decades, δ13C raised 2.4 and 2.6‰, while Cmaize increased 1.6 and 2.2 g kg−1 in MS and MG systems, respectively. The estimated average humification coefficient over this period of maize-C was 0.11 for the MS system, about twice as that of the MG system (0.06). This reconfirms findings of stronger contribution of belowground biomass versus aboveground residues to stabilized SOC pools over the medium to long term. By the end of the incubation, on average 10.4% and 11.6% of Cmaize had been decomposed in the MS and MG soils, respectively. These Cmaize mineralization rates were statistically equal for the two systems, which indicates that mainly belowground biomass remained in the soils. Also, net N mineralization was indifferent to the crop rotations (MS: 58.8 mg N kg−1 and MG: 52.6 mg N kg−1). To reconcile the two main observations in this study, we hypothesize that the lower preservation of shoot-C could be manifested on a shorter term. Detailed research is needed to determine the time scale of increased stabilization of root-C versus shoot-C under field conditions.

Catch crops may strongly reduce nitrate leaching during autumn and winter in temperate climates. Authorities therefore aim to stimulate farmers to place catch crops in their rotations by allowing them to apply more nitrogen (N) to their fields. Furthermore, some regulations make it possible to fertilize catch crops after harvest of specific crops such as winter cereals, even if catch crops are sown during late summer. Some farmers claim that this practice is essential for a good development of the catch crop. However, it is not sure whether this summer fertilization to catch crops could result in any additional nitrate leaching, compared to nitrate leaching under non-fertilized catch crops. We therefore designed field experiments including four different catch crop species, each of them sown after harvest of winter cereals at two different dates, and each of them receiving two different doses of pig slurry or receiving no fertilizer at all. Experiments were installed on sites with different soil textures in northern Belgium. Based on the results of soil mineral N and N uptake, we assessed the risk of additional nitrate leaching caused by fertilization of catch crops. We found that the apparent uptake of N released from pig slurry was rather limited but sufficient to avoid additional nitrate leaching on sandy soils, mainly due to supplementary immobilization of the applied N occurring during mineralization of the cereal crop residues. It is critical to mention the limiting conditions that we found to be adequate from our results: catch crops were to be sown in good circumstances before September and could only receive the smallest dose of pig slurry, which was approximately 60 kg N ha−1. On silty soils, however, we found even under these conditions a few indications of small amounts of additional nitrate leaching. As fertilization did not seem mandatory to develop an effectively functioning catch crop and as there was no indication of reduced nitrate losses due to this practice, we would rather discourage fertilization of catch crops to exclude any environmental risk. However, fertilization significantly increased the catch crop yield, so the decision to fertilize or not may also be seen as a trade-off between minor amounts of additional nitrate leaching and enhanced biomass-related effects, such as the additional input of organic carbon into the soil.

Sustainable agriculture requires the careful optimization of the use of organic amendments to improve soil fertility while minimizing any harmful environmental effects. To understand the events that occur in soil after the addition of different organic amendments, we evaluated the nitrogen (N) mineralization dynamics in soil after adding organic amendments, and evaluated changes in the microbial population. The four organic amendments were fresh dairy cattle manure, fresh white clover, vegetable, fruit, and yard waste compost, and poplar tree compost. The N mineralization potential of each organic amendment was determined by analyzing total mineral nitrogen during a 97-day laboratory incubation experiment. Soils amended with clover released 240 μg N g −1 soil during the 97-day incubation, more than twice as much as that released from soils amended with manure or composts (76–100 μg N g −1 soil). At the end of the incubation, the net N mineralization in clover-amended soils was 54%, more than five times higher than that in soils amended with composts or manure (4%–9%). Nitrogen was mineralized faster in clover-amended soil (1.056 μg N g −1 soil day −1 ) than in soil amended with composts (0.361–0.417 μg N g −1 soil day −1 ). The microbial biomass carbon content was higher in clover-amended soil than in the soils amended with manure or composts. We monitored changes in the microbial population in amended soils by a phospholipid fatty acid (PLFA) analysis. On day 97, there were higher concentrations of total PLFAs in soils with organic amendments (e.g., 14.41 nmol g −1 in clover-amended soil) than in control soil without amendments (9.84 nmol g −1 ). Bacteria (Gram-positive and Gram-negative), actinomycetes, and fungi were more abundant in clover-amended soils than soils amended with manure or composts. The N mineralization potential varied among the four organic amendments. Therefore, the timing of application and the type of organic amendment should be matched to the nutrient needs of the crop.

N fertilization is often viewed as a cheap insurance against yield loss in vegetable production because of the generally large added value, resulting in application of fertilizer N often in excess of actual crop demand. In combination with the low fertilizer N recovery by many vegetable crops and the often excessive irrigation, this may lead to both health and environmental risks related to high nitrate concentrations in water leaving the root zone. In this review, we discuss the decisive factors in the overall N balance of field vegetable production systems and the different tools at hand to increase fertilizer use efficiency and consequently reduce N losses to the environment. Based on this, we identify areas of research and technology transfer where further work is required. Only an integration of the different methods and strategies for N management may really mitigate the risk of nitrate leaching and maintain crop yields while enhancing the environmental sustainability of vegetable production systems.

In north-west Europe, agricultural diffuse P losses are a major cause of eutrophication problems in surface waters. Given that the Water Framework Directive (WFD) demands fast water quality improvements and most of the actual P mitigation strategies tend to work on the long run, new short-term mitigation measures are urgently needed. We here report on the entire process of developing small scale field filters to remove P at the end of tile drains, starting from the screening of potential P sorbing materials (PSM): iron coated sand (ICS), acid pre-treated natural minerals (biotite, glauconite and olivine) and bauxite. Initial batch (ad)sorption experiments revealed following order in both, P sorption capacity and speed: ICS > bauxite > glauconite > olivine = biotite. Because of the presence of significant amounts of lead and/or nickel, we excluded bauxite and olivine from further experiments. Subsequent lab scale flow through systems were conducted with P filters containing mixtures of ICS and glauconite (100/0, 90/10, 80/20, 70/30 and 60/40%, respectively, on weight basis). We found a significant relationship between Ksat and the filter mixtures particle size distribution and bulk density, and a significant effect of the filter mixture composition on P removal efficiency and stability of Ksat. During the 10 week field trials, the pure ICS filters were capable of processing all drainage discharge rates (up to 6 m3 day−1) with a P removal efficiency of ≥74%. The 90/10 ICS/glauconite filters could process up to 4 m3 water day−1 with a P removal efficiency of 57%. As saturated ICS filters can easily be replaced and recycled for other applications, this is a promising sustainable technique to drastically cut back diffuse P losses and to tremendously improve surface water quality in the short term.

To restore species-rich terrestrial ecosystems on ex-agricultural land, establishing nutrient limitation for dominant plant growth is essential because in nutrient-rich soils, fast-growing species often exclude target species. However, N-limitation is easier to achieve than P-limitation (because of a difference in biogeochemical behavior), biodiversity is generally highest under P-limitation. Commonly used restoration methods to achieve low soil P-concentrations are either very expensive or take a very long time. A promising restoration technique is P-mining, an adjusted agricultural technique that aims at depleting soil-P. High biomass production and hence high P-removal with biomass are obtained by fertilizing with nutrients other than P. A pot experiment was set up to study P-mining with Lolium perenne L. on sandy soils with varying P-concentrations: from an intensively used agricultural soil to a soil near the soil P-target for species-rich Nardus grassland. All pots received N- and K-fertilization. The effects of biostimulants on P-uptake were also assessed by the addition of arbuscular mycorrhiza (Glomus spp.), humic substances or phosphate-solubilizing bacteria (Bacillus sp. and Pseudomonas spp.). In our P-rich soil (111 µg POlsen/g), P-removal rate was high but bioavailable soil-P did not decrease. At lower soil P-concentrations (64 and 36 µg POlsen/g), bioavailable soil-P had decreased but the P-removal rate had by then dropped 60% despite N- and K-fertilization and despite that the target (

To evaluate the effect of farming system on gaseous emission of N from soil, the measurements of nitrous oxide (N2O) were taken in organic and conventional paddy fields in tropics. Eleven soil samples from organic and neighboring conventional sites in Central Java, Indonesia were incubated at two different moisture contents expressed as water filled pores (WFPS), namely 75% WFPS and 100% WFPS. Emission of N2O-N at 75% WFPS was significantly higher in conventional management than in organic management. At 100% WFPS, the N2O-N emission was also higher in conventional than in organic farming system. Although it was not significantly different, it has significantly and positively correlations with SOC, total N and initial mineral N content. Due to the swelling ability of the high clay which is contained in soil samples, less N2O-N emission in 75% WFPS than in 100% WFPS was observed in the present study. The range of N2O-N emission at 75% WFPS was 0.01 – 0.03 kg N2O-N/ha in organic farming and 0.005 – 0.16 kg N2O-N/ha in conventional farming; for organic farming at 100% WFPS, the N2O-N emission was 0.04 – 61 kg N2O-N/ha and in conventional farming was 0.08 – 74 kg N2O-N/ha. This study concludes that organic farming in paddy fields might have more promising potential to mitigate N2O-N emission than conventional farming in paddy fields.

Vegetable crop residues take a particular position relative to arable crops due to often large amounts of biomass with a N content up to 200 kg N ha−1 left behind on the field. An important amount of vegetable crops are harvested during late autumn and despite decreasing soil temperatures during autumn, high rates of N mineralization and nitrification still occur. Vegetable crop residues may lead to considerable N losses through leaching during winter and pose a threat to meeting water quality objectives. However, at the same time vegetable crop residues are a vital link in closing the nutrient and organic matter cycle of soils. Appropriate and sustainable management is needed to harness the full potential of vegetable crop residues. Two fundamentally different crop residue management strategies to reduce N losses during winter in intensive vegetable rotations are reviewed, namely (i) on-field management options and modifications to crop rotations and (ii) removal of crop residues, followed by a useful and profitable application.

Soil quality in vegetable cropping systems is seriously threatened by intensive tillage and fertilization practices and by limited crop rotations. Inclusion of cover crops, compost application and reduced tillage may help to sustain soil quality. A three-year field trial was set up on horticultural land to explore the combined effects of compost amendment at three rates (0, 15 and 45 Mg ha−1 year−1) and tillage practices (reduced tillage versus conventional ploughing) on soil quality. Cover crop was not a factor in the experiment, but cover crops were included in the rotation for reasons of good agricultural practice. The highest compost dose supported the initial level of total organic carbon in the arable layer. The decrease in pH in the arable layer was considerably limited by compost application, irrespective of the dose applied. Reduced tillage resulted in a favorable stratification for different soil quality indicators both by placement of organic inputs near the soil surface and by a reduction of leaching of base cations and organic carbon compounds. Differences between tillage practices and compost doses were most striking in the 0–10 cm soil layer. Compost application at the highest rate enhanced organic C content by 16% compared to the content in the non-amended soil. Reduced tillage induced a 13% higher organic C content in the 0–10 cm soil layer than that in the underlying 10–30 cm layer. Combining reduced tillage and recurrent compost application resulted in a different soil microbial community structure in the 0–10 cm surface layer, as revealed by phospholipid fatty acids analysis. Total microbial biomass was 44% higher under reduced compared to conventional tillage and increased by 27% due to compost application at a rate of 45 Mg ha−1 year−1. Fungal biomass doubled in the surface layer by reduced tillage. Actinomycetes and arbuscular mycorrhizal fungi were favored by both reduced tillage and compost application. Conversion to reduced tillage allowed for sustaining crop production in this intensive vegetable cropping system. Compost application and reduced tillage counteracted soil degradation.

Judicious management of organic matter supply and tillage practice is crucial for sustaining soil quality in horticulture. We have studied whether N fertilization of vegetable crops should be adapted in the short term when soil management changes to include compost application and reduced tillage as soil quality improving factors. The experimental setup was a multiyear field trial on a sandy loam soil with a vegetable crop rotation. Soil tillage in spring was either conventional (moldboard plough) or reduced, non-inversion tillage (with a specially designed chisel plough). Starting in 2008, farm compost was applied each autumn at three rates: 0, 15 and 45 Mg per hectare. The three-year crop rotation (2009–2011) consisted of broccoli ( Brassica oleracea , var. Italica Group), carrots ( Daucus carota ) and leek ( Allium porrum ). Small but significant differences in N dynamics were found between treatments. Broccoli had a higher N uptake and biomass production under reduced compared to conventional tillage. In accordance with this, the apparent net N mineralization tended to be higher for reduced tillage compared to conventional tillage. In contrast, for leek, N uptake did not differ between tillage practices despite a higher apparent net N mineralization under conventional tillage. A tendency for a higher biomass production under conventional tillage was in line with a tendency for a higher amount of residual soil mineral N that might have increased the risk of N losses. In the carrot crop, a higher amount of mineral N under conventional tillage did not increase root yield. Compost application maintained soil organic matter content and did not result in a higher amount of residual soil mineral N. Only in the carrot growing season, compost application increased soil mineral N content to a limited extent. The small short-term changes in overall N availability observed between treatments do not necessitate changes in N fertilization strategy or additional precautions regarding residual soil mineral N.

This study, aiming to unravel whether topsoil conditions under tree species with nutrient-poor leaf litter can be altered by admixing a shrub layer, was performed in 12 pine (mainly Pinus sylvestris) and 12 oak (Quercus robur) stands on sandy podzolic soils in north-east Belgium. We examined the effects of presence of a shrub layer on forest floor mass and topsoil chemical properties related to soil acidification. The shrub species included were European rowan (Sorbus aucuparia), alder buckthorn (Rhamnus frangula) and black cherry (Prunus serotina). For each tree species, 60–90 years old stands were selected containing shrubs present in varying cover classes: sparse ( 70%). The oak stands were characterized by less but ‘nutrient-richer’ litterfall, compared to the pine stands. This was reflected in less humus build-up (FH-horizon) and higher pH, CEC, BS and lower C/N in the topsoil in the oak stands compared to the pine stands. However, despite the fact that the shrubs produced litter with significantly higher base cation and N concentrations than that of the studied tree species, we did not find any significant changes in topsoil conditions in the pine and oak stands under study, even under dense shrub layers (87–91% cover).

Rangeland degradation is a serious problem throughout sub-Saharan Africa and its restoration is a challenge for the management of arid and semi-arid areas. In Lake Baringo Basin of Kenya, communities and individual farmers are restoring indigenous vegetation inside enclosures in an effort to combat severe land degradation and address their livelihood problems. This study evaluated the impact of enclosure management on soil properties and microbial biomass, being key indicators of soil ecosystem health. Six reseeded communal enclosures using soil embankments as water-harvesting structures and strictly regulated access were selected, varying in age from 13 to 23 years. In six private enclosures, ranging from 3 to 17 years in age, individual farmers emulated the communal enclosure strategy and restored areas for their exclusive use. Significant decreases in bulk density, and increases in the soil organic carbon, total nitrogen and microbial biomass contents and stocks were found in the enclosures as compared with the degraded open rangeland. In the private enclosures, the impact of rehabilitation on the soil quality was variable, and soil quality was in general lower than that obtained under communal management. The significant increase of absolute stocks of carbon, nitrogen and microbial biomass compared to the degraded open rangeland indicates the potential for the restoration of soil quality through range rehabilitation. Over-sowing with indigenous legume fodder species could improve total nitrogen content in the soil and nutritional value of the pastures as well.

The application rate of poultry manure as organic fertilizer is restricted due to its low C/P and N/P ratio. This research was set up to find out optimal feedstock composition for composting chicken manure in order to create a soil improver with a higher value as organic fertilizer, and to assess the effects of this process on P availability in the end products. The research is based on two compost experiments with three treatments each, and the chicken manure composts were compared with the end products of green waste compost used as bedding material in chicken houses, centrally processed chicken manure and a stockpiled mixture of green waste compost and chicken manure. In the first compost trial, feedstock materials were compared for composting with fresh chicken manure. The chicken manure compost with 42.5 vol% bark in the feedstock had the highest quality as soil improver in terms of organic matter content, C/P ratio, C/N ratio and stability. Results of the second compost trial indicate that 10 vol% of fresh chicken manure is the upper limit in small-scale on-farm windrow composting above which nutrient losses become too high and the N/P ratio of the obtained fertilizer becomes too low. Stability of the product (expressed as oxygen uptake rate) had a major effect on P availability in the compost. Blending the chicken manure compost with biochar based on holm oak resulted in a more than proportional decrease in easily available P in the biochar-blended compost. P in poultry manure can be recycled through composting and be applied as an organic fertilizer with optimal nutrient ratio and organic matter content when appropriate feedstock materials are selected and the amount of fresh manure in the feedstock mixture is restricted.

In Cuba there is a strong differentiation in types of farming systems that operate at very different levels of management intensity. The aim of this research was to characterize differences in soil quality caused by different agricultural management systems and the effects of seasonality on soil chemical and biological indicators within representative farming systems in Santa Clara municipality, Villa Clara Province, Cuba. Two state farms, two cooperative farms, and three private farms, all located on brown calcareous soils, which differed in soil management and technological complexity were selected. Soil samples from two fields of each farm were collected to a depth of 20 cm. Laboratory analysis were performed to determine physical (aggregate stability, plasticity, and permeability), chemical (pH and organic matter), and biological (dehydrogenase and -glucosidase activities) indicators of soil quality. We found significant differences in soil quality among the three farming systems, which were most pronounced between private and state farms, with respect to physical soil properties (aggregate stability and plasticity) and the activity of enzymes. Seasonality also exerted an important influence on the activities of dehydrogenase and -glucosidase, which were greater in the rainy season. As a conclusion, we can say that the differences in soil management between the farming systems were reflected in consistent differences in soil quality indicators, notably between the state and private farms.

Conservation agriculture (CA) characterised by minimal soil disturbance, permanent soil surface cover by dead or living plants and crop rotations is one way of achieving higher soil organic carbon (C) in agricultural fields. Sandy loam and loamy soil samples from zero tillage (ZT) and conventional tillage (CT) plots were taken from farmers’ fields during the dry season in August 2006. Soil organic carbon (SOC) and soil organic nitrogen (SON), microbial biomass carbon (MB-C) and microbial biomass nitrogen (MB-N), C mineralization and SOC distribution in particle size fractions in 0–20 cm layer were evaluated. Forty eight farmers’ fields were randomly sampled at four different locations in Central and Northern Malawi, representing ZT plots maintained for a different number of years, and ten fields under CT with similar soil type and crop grown were selected. SOC and SON in ZT fields were 44 and 41 % (4 years ZT) and 75 and 77 % (5 years ZT) higher, respectively, than CT plots. MB-C and MB-N in ZT fields were 16 and 44 % (4 years ZT) and 20 and 38 % (5 years ZT) higher, respectively, than CT plots. However, MB-C and MB-N in ZT fields were 27 and 25 % (2 years ZT) and 17 and 9 % (3 years ZT) lower than in CT plots. The proportion of the total organic C as microbial biomass C was relatively higher under CT than ZT treatments. The higher SOC and MB-C content in the ZT fields resulted in 10, 62, 57 % higher C mineralization rate in ZT plots of 3, 4 and 5 years of loamy sand soils and 35 % higher C mineralization rate in ZT plot of 2 years than CT of sandy loam soils in undisturbed soils in the laboratory. Simulating plough from the undisturbed soils that were used for C mineralization experiment resulted in linear curves indicating that all organic C was already depleted during the first incubation period. The relative distribution of soil organic matter (SOM) in silt and clay size fractions was strongly correlated (r = 0.907 and P ≤ 0.01) with silt percentages. Easily degradable carbon pool (CA,f) was correlated (r = 0.867 and P ≤ 0.05) with organic carbon in sand size fraction. In developing viable conservation agriculture practices to optimize SOC content and long-term sustainability of maize production systems, priority should be given to the maintenance of C inputs, crop rotations and associations and also to reduced soil disturbance by tillage.

A change in land use from agriculture to forest generally increases soil acidity. However, it remains unclear to what extent plant traits can enhance or mitigate soil acidification caused by atmospheric deposition. Soil acidification is detrimental for the survival of many species. An in-depth understanding of tree species-specific effects on soil acidification is therefore crucial, particularly in view of the predicted global increases in acidifying nitrogen (N) deposition. Here, we report soil acidification rates in a chronosequence of broadleaved deciduous forests planted on former arable land in Belgium. This region receives one of the highest loads of potentially acidifying atmospheric deposition in Europe, which allowed us to study a ‘worst case scenario’. We show that less than four decades of forest development caused significant soil acidification. Atmospheric deposition undoubtedly and unequivocally drives postagricultural forests towards more acidic conditions, but the rate of soil acidification is also determined by the tree species-specific leaf litter quality and litter decomposition rates. We propose that the intrinsic differences in leaf litter quality among tree species create fundamentally different nutrient cycles within the ecosystem, both directly through the chemical composition of the litter and indirectly through its effects on the size and composition of earthworm communities. Poor leaf litter quality contributes to the absence of a burrowing earthworm community, which retards leaf litter decomposition and, consequently, results in forest-floor build-up and soil acidification. Also nutrient uptake and N2 fixation are causing soil acidification, but were found to be less important. Our results highlight the fact that tree species-specific traits significantly influence the magnitude of human pollution-induced soil acidification.

Nitrogen fertilizer application rates in intensive vegetable production in (South) East Asia have increased exponentially over the past decades, including in the low income countries. While there have been reports of excessive N inputs from e.g. Vietnam, Thailand and Indonesia, very little quantitative knowledge exists on the real extent of the problem. We calculated N balances and agronomic N use efficiencies (ANUE) for a number of typical intensive vegetable rotations in the highlands of Central Java, Indonesia, on fertile Andisols, both for individual cropping cycles (short term) as for 6 consecutive cropping cycles (long term). This was done for farmers practice (FP) treatments, and improved practice (IP) treatments, where N fertilization was significantly reduced. Yields were in general similar in FP and IP, but tended to be slightly higher in IP, with some significant differences. Both the short and long term N balances were always positive and usually very high. Short term N balances ranged from 9 to 559 kg N ha−1 and 219 to 885 kg N ha−1 in IP and FP, respectively, while short term ANUE ranged from 8 to 67 and 4 to 39% in IP and FP, respectively. Long term N balances ranged from 627 to 1,885 kg N ha−1 and 962 to 3,808 kg N ha−1 in IP and FP, respectively, indicating a massive excess of N supply especially in FP. N balances can thus be drastically reduced with no negative impacts on yield, on the contrary. Soil mineral N in the 0–25 cm layer was in general not very high (6.5–38.8 mg N kg−1 soil) and not systematically different between IP and FP, probably as a result of excessive NO3 − leaching. Therefore, topsoil mineral N seems to have only limited indicator value under these conditions. Because denitrification losses in these soils are not very high, most N in excess of the crop requirements will be lost by leaching. Quantitative data on N balances as obtained here may be used to sensitize policy makers and farmers about the threat of current farming practices to the environment, and to improve economic performance.

We compared the effect of organic and conventional farming practices on soil microbial dynamics in West Java, Indonesia. A secondary forest was included to obtain natural reference values. On the organic farms, soil fertility is maintained mainly with composted organic matter in contrast to conventional farmers who combine fresh manure and chemical fertilizers, and typically apply large amounts of pesticides. Parameters measured were dehydrogenase, β-glucosidase, acid phosphomonoesterase and β-glucosaminidase activity, microbial biomass C (MBC) and microbial community composition by phospholipid fatty acid analysis. A strong negative impact of intensive chemical fertilizer and pesticide use on soil enzyme activities was demonstrated. Dehydrogenase and β-glucosidase activities were correlated with soil organic matter content and pH. β-glucosidase activity under organic management approached that under forest, while MBC and dehydrogenase activity remained higher under forest. The composition of the soil microbial community strongly differed between forest and cultivated soil, a clear difference in composition was also observed between conventional and organic farming. Dehydrogenase activity and C16:1ω5c, marker fatty acid for arbuscular mycorrhizal fungi, appeared to be particularly suited as indicators of the impact of management on soil quality and on the soil microbial community.

Total soil organic-carbon (SOC) stocks for grassland soils in Flanders (N Belgium) were determined for the Kyoto Protocol reference year 1990 and 2000 in order to investigate whether these soils have been CO2 sinks or sources during that period. The stocks were calculated by means of detailed SOC datasets, which were available at the community scale for the whole of Flanders. The total SOC stocks for Flemish grassland soils (1 m depth) were estimated at 38 Mt SOC in 1990 and 34 Mt SOC in 2000. The loss of SOC resulted from a decrease in the SOC content of grassland soils (71%) and could also partly (29%) be explained by a decline in grassland area. Significant decreases in %SOC for the 0–6 cm depth layer were found for the 1990s for the coarser-textured soils with SOC losses ranging between –0.3% and –0.5% over the 10 y period. Specific management practices that disturb the SOC balance such as conversion to temporary grassland and a reduction of animal-manure application are hypothesized to have contributed to the observed loss of SOC stocks. We furthermore conducted an analysis of uncertainty of the 1990 and 2000 grassland SOC–stocks calculation using Monte Carlo analysis. Probability-distribution functions were determined for each of the inputs of the SOC-stock calculation, enabling us to assess the uncertainty on the 1990 and 2000 SOC stocks. The frequency distributions of these simulated stocks both closely approached lognormal distributions, and their 95%-confidence intervals ranged between 150% and 50% of the calculated mean SOC stock. The standard error on the measured decrease in SOC stocks in Flemish grassland soils during the 1990s was calculated to be 7–8 Tg SOC, which is equivalent to twice this decrease. This clearly shows that large-scale changes in SOC stocks are uncertainty-ridden, even when they are based on detailed datasets.

Reduced tillage (RT) agriculture is an effective measure to reduce soil loss from soils susceptible to erosion in the short-term and is claimed to increase the soil organic carbon (SOC) stock. The change in distribution and total SOC stock in the 0–60 cm layer, the stratification of microbial biomass carbon (MB-C) content in the 0–40 cm layer and the carbon (C) mineralization in the upper 0–5 cm layer in silt loam soils in Western Europe with different periods of RT agriculture were evaluated. Ten fields at seven locations, representing the important RT types and maintained for a different number of years, and eight fields under conventional tillage (CT) agriculture with similar soil type and crop rotation were selected. RT agriculture resulted in a higher stratification of SOC in the soil profile than CT agriculture. However, the total SOC stock in the 0–60 cm layer was not changed, even after 20 of years RT agriculture. The MB-C was significantly higher in the 0–10 cm layer under RT agriculture, even after only 5 years, compared to CT agriculture. The higher SOC and MB-C content in the upper 0–5 cm layer of RT fields resulted in a higher C mineralization rate in undisturbed soil in the laboratory. Simulating ploughing by disturbing the soil resulted in inconsistent changes (both lower and higher) of C mineralization rates. A crop rotation with root crops, with heavy soil disturbance every 2 or 3 years at harvest, possibly limited the anticipated positive effect of RT agriculture in our research.

ARTICLE I NFO Soil erosion from agricultural lands is a serious problem on the Chinese Loess Plateau. In total, 28 field rainfall simulations were carried on loamy soils under different management practices, namely conventional tillage (CT), no till with mulch (NTM), reduced tillage (RT), subsoiling with mulch (SSM), subsoiling without mulch (SS), and two crops per year (TC), to investigate (i) the effects of different soil management practices on runoff sediment and (ii) the temporal change of runoff discharge rate and sediment concentration under different initial soil moisture conditions (i.e. initially dry soil surface, and wet surface) and rainfall intensity (85 and 170 mm h �1 ) in the Chinese Loess Plateau. NTM was the best alternative in terms of soil erosion control. SSM reduced soil loss by more than 85% in 2002 compared to CT, and its effects on runoff reduction became more pronounced after 4 years consecutive implementation. SS also reduced considerably the runoff and soil loss, but not as pronounced as SSM. TC resulted in a significant runoff reduction (more than 92%) compared to CT in the initial 'dry' soil, but this effect was strongly reduced in the initial 'wet' soil. Temporal change of runoff discharge rate and sediment concentration showed a large variation between the different treatments. In conclusion, NTM is the most favorable tillage practices in terms of soil and water conservation in the Chinese Loess Plateau. SSM can be regarded as a promising measure to improve soil and water conservation considering its beneficial effect on winter wheat yield.

The effect of reduced tillage (RT) on nitrous oxide (N2O) emissions of soils from fields with root crops under a temperate climate was studied. Three silt loam fields under RT agriculture were compared with their respective conventional tillage (CT) field with comparable crop rotation and manure application. Undisturbed soil samples taken in September 2005 and February 2006 were incubated under laboratory conditions for 10 days. The N2O emission of soils taken in September 2005 varied from 50 to 1,095 µg N kg−1 dry soil. The N2O emissions of soils from the RT fields taken in September 2005 were statistically (P

Nutrient dynamics in wetland ecosystems are largely controlled by soil moisture content. Therefore, the influence of soil moisture content on N mineralization should be explicitly taken into account in hydro-ecological models. The aim of this research was to establish relationships between N mineralization and soil moisture content in loamy to silty textured soils of floodplain wetlands in central Belgium. Large undisturbed soil cores were taken, incubated for 3 months under various moisture contents, and zero order and first order N mineralization rates were calculated. We used the percentage water-filled pore space (WFPS) as an expression of soil moisture because it is a better index for aeration dependent biological processes than volumetric moisture content or water retention. The relationship between the N mineralization rate and %WFPS was described by a Gaussian model. The optimum WFPS for N mineralization ranged between 57% and 78%, with a mean of 65% ± 6% WFPS. Expected annual net N mineralization rates at field temperature (9.7°C) and at optimal moisture content varied between 30 and 186 kg N ha-1 (0–15 cm depth) year-1, with a mean of 110 ± 42 kg N ha-1 (0–15 cm) year-1. The mean N turnover rate amounted to 2.3 ± 1.1 g N 100 g-1 N year-1. Multiple linear regressions between N mineralization and general soil parameters showed that soil structure has an overriding impact on N mineralization in wetland ecosystems.

In the scope of the increasing concern for soil conservation, reduced tillage (RT) agriculture is growing more important in today’s agriculture in Western Europe. However, crop rotations often include beets and potatoes, crops that are generally assumed to be less suitable under RT agriculture because they result in a high disturbance of the soil at the formation of the ridges and at harvest. Therefore, the short- and long-term effect of RT agriculture on bulk density (BD), water retention curve (WRC), aggregate stability and field-saturated hydraulic conductivity of silt loam soils with crop rotations including root crops was evaluated. Ten fields at seven locations representing the important RT types, applied for a different number of years, and eight fields under conventional tillage (CT) agriculture with similar soil type and crop rotation were selected. At each location, BD of the 5–10 cm layer was mostly lower in the RT fields (1.42 � 0.05 Mg m � 3 [average with

Crop rotations in Western Europe contain crops that seem not suitable for reduced tillage (RT) agriculture because they often include beets and potatoes, resulting in a high disturbance of the soil at the formation of the ridges and at harvest. Therefore, the short- and long-term effects of RT on the stratification and stock of total nitrogen (TN) in the 0–40 cm depth layer and the nitrogen (N) mineralization in the upper 15 cm depth layer of silt loam soils was evaluated. For doing so, 10 fields at seven locations representing the important types of RT systems in Belgium, applied for a different number of years, and eight fields under conventional tillage (CT) with comparable soil type and crop rotation were selected. Despite the presence of root and tuber crops in these rotations, the stratification of the percentage of TN and of the carbon to nitrogen ratio was more pronounced under RT than CT fields. The TN stock in the RT fields worked with a cultivator or soil loosener was comparable to CT fields, even after 20 years. No trend could be found in the change in TN stock of reduced tillage by direct drilling compared to CT. The N mineralization rate in undisturbed soil cores under controlled conditions in the laboratory was on average 0.20 ± 0.08 mg N kg −1 dry soil day −1 for RT fields compared to an average of 0.13 ± 0.05 mg N kg −1 dry soil day −1 for CT fields. This increase in N mineralization rate was correlated with a higher microbial biomass nitrogen content.

Compost and other organic amendments have been proven to improve the soil physical quality. In Flanders, vegetable, fruit and garden (VFG) wastes are collected selectively and composted. We studied the effects of the combined application of three different doses of VFG compost and cattle slurry and one treatment with only mineral N applied, during 9 years on a range of soil physical properties: aggregate stability, saturated hydraulic conductivity, bulk density, total pore volume and soil moisture retention. The organic amendments had a significantly beneficial impact (p

Field experiments were carried out to study the effects of different soil management practices on the water balance, precipitation use efficiency (PUE), and crop yield (i.e. winter wheat and peanut) on a loess soil near Luoyang (east edge of the Chinese Loess Plateau, Henan Province, China). Field plots were set up in 1999 including following soil management practices: subsoiling with mulch (SS), no-till with mulch (NT), reduced tillage (RT), two crops per year (i.e. winter wheat and peanut, TC), and a conventional tillage control (CT). The field plots were equipped to monitor all components of the soil–water balance except evapotranspiration, which was computed by solving the water balance equation. The results showed that although soil management had smaller influence on the magnitude of the water balance components than did precipitation variations, small influences of the applied soil management practices on water conservation during the fallow period can greatly affect winter wheat yield. SS increased consistently precipitation storage efficiency (PSE) and PUE over the 5 years compared to CT except during the wettest year. NT also had a noticeable effect on postharvest water storage during the fallow period; however, the influence on yield of NT depended on the amount of precipitation. TC lowered the winter wheat yield mainly due to the unfavorable soil moisture conditions after growing peanut in summer; however, the harvested peanut gained an extra profit for the local farmer. No matter which kind of soil management practices was adapted, PSE never exceeded 41.6%, which was primarily attributed to high evapotranspiration. From data of five consecutive agricultural years between 2000 and 2005, it could be concluded that SS resulted in the highest PSE, PUE and crop yield. TC also showed promising results considering the economic value of the second crop. NT performed slightly less as SS. CT gave intermediate results, whereas RT was the worst alternative.

The farm gate nutrient balance approach has improved nutrient management in Western-European countries by re-examining the routine agricultural practices. This paper reports on the farm gate nitrogen (N) and phosphorus (P) balances of typical Hungarian arable and mixed farms calculated for 2002–2004. The farm gate nutrient surpluses/deficits varied a great deal between the farms within 1 year and between the different years for one farm. This could partly be explained by the stock changes. The N and P balances calculated hypothetically (assuming increased or decreased purchase instead of an increase or decrease of stock of roughage, concentrates, manure, mineral fertilizers and seeds and presuming increased or decreased sales instead of an increase or decrease of stock of animals, animal products and plant products) clearly reflected the lower grain crop yields in 2003 due to the dry weather circumstances, especially for the arable farms. The east–west divide in Hungarian agriculture was shown in the total inputs and surpluses of N. The low farm gate P surpluses or even deficits of most selected farms indicate soil mining and are a warning for possible future crop deficiencies and yield reduction.

Several recent reports on cropland soil organic carbon (SOC) stock changes throughout Europe indicate a general continuing loss of SOC from these soils. As most arable soils in Europe are not in an equilibrium situation because of past changes in land-use and management practices, shifts in both have been suggested to drive this decline of SOC stocks. A lack of data has prevented the unambiguous verification of the contribution of these factors to SOC loss. First, this study focused on recent evolutions in management options for SOC sequestration in Flanders and showed that despite such practices have increased since 1990, their current contribution is still limited. Strikingly, their expansion is at odds with the reported general losses of SOC (−0.48 t OC ha−1 year−1 on average). We used very detailed datasets of livestock numbers, N-application rates and cropping surfaces to calculate regional shifts in input of effective OC from animal manure application, cereal straw incorporation and crop residue incorporation which amounted to −0.094, −0.045 and −0.017 t OC ha−1 year−1, respectively. Shifts in management were identified to have potentially brought about but a third of the recent loss of SOC in the study area, although for central West-Flanders and the Eastern border of Flanders larger impacts of management were observed. This study suggests other influences such as land-use change and climate change to be involved as well. We estimated that another 10%–45% of the loss of SOC could potentially be attributed to land-use changes from grassland to cropland during the 1970–1990 period and about 10% to the observed temperature increase. While being a regional-scaled case study, these findings may be relevant to other European regions in particular (Denmark, The Netherlands, North-West Germany, Brittany and the North-West of France, the Po-valley in Italy and parts of England), with similar climate and intensity of agriculture, and where comparable trends in farming management may well have taken place.

At the moment, Hungarian agriculture is confronted with a certain duality as far as nutrients are concerned. On the one hand, national soil nutrient balances show substantial deficits, and on the other hand, agricultural nutrient use is responsible for a part of the nitrogen (N) and phosphorus (P) losses to the environment. To understand this duality and help optimize farm nutrient management, the farm gate N and P balances of 12 farms, representing a variety of Hungarian agriculture, were calculated for the year 2002. The farm gate N and P surpluses/deficits in the east of the country were lower than in the west. This was correlated with a lower fertilization rate. The low soil fertility level due to a prolonged period of low fertilization in combination with continuing nutrient deficits can lead to possible future reduction in crop yields.

Changes in the physical distribution (particle size and the state stability against decomposition) of the organic carbon pool in tilled layers of Hungarian field soil under different tillage treatments were studied. Three years after starting the experiment, soil samples were fractionated (they were taken in March 2005) by their particle size and density. The treatments caused well measurable, significant effects on two fractions of intra-microaggregate organic matter (53-250μm particle-sized, well and less decomposition-resistant pools) and onto their relative rate in the organic carbon pool of the whole soil.Different tillage treatments caused different distributions in the organic matter fractions. In regularly intensely cultivated soils evolve different physical structure, particle size-distribution, which reduce the soil fertility and its resistance against outer impacts.

The denitrification potential of the soil horizons between 0- and 90-cm depth of 20 agricultural fields, representative of the most frequent combinations of agricultural crops and soil textures in Flanders (Belgium), and the factors affecting the denitrification potential were studied in the laboratory under controlled conditions. The denitrification potential in the presence of an added soluble C and N source was measured at 15°C after saturation of air-dried soil samples with water. The denitrification potential of the lower horizons was generally negligible compared to the upper horizons. The lower denitrification potential of the deeper horizons could partially be explained by their limited C availability. The denitrification potential of the upper horizons strongly depended on texture. Based on this parameter the soils could be divided into three groups: soils with a high clay content (>30% clay) were characterised by a high denitrification potential (>8.33 µg N g-1 dry soil day-1); soils with medium texture had a medium denitrification potential, between 0.41 and 7.25 µg N g-1 dry soil day-1; and soils with a high sand content (>80% sand) had a low denitrification potential (

Evaluations of soil organic carbon (SOC) stocks are often based on assigning a carbon density to each one of a number of ecosystems or soil classes considered, using data from soil profiles within these categories. A better approach, in which the use of classification methods by which extrapolation of SOC data to larger areas is avoided, can only be used if enough data are available at a sufficiently small scale. Over 190 000 SOC measurements (0–24 cm) have been made in the Flemish cropland (the Northern part of Belgium) in the 1989–2000 period. These SOC data were grouped into 3-year periods and as means plus standard deviation per (part of) community (polygons). This large dataset was used to calculate SOC stocks and their evolution with time, without data extrapolation. Using a detailed soil map, larger spatial groups of polygons were created based on soil texture and spatial location. Linear regression analysis showed that in the entire study area, SOC stocks had decreased or at best had remained stable. In total, a yearly decrease of 354 kton OC yr−1 was calculated, which corresponds with a net CO2 emission of 1238 kton CO2 yr−1. Specific regions with a high carbon sequestration potential were identified, based on SOC losses during the 1989–2000 period and the mean 1999 SOC content, compared to the average SOC content of soils in Flanders with a similar soil texture. When restoring the SOC stocks to their 1990 level, we estimated the carbon sequestration potential of the Flemish cropland soils to be some 300 kton CO2 yr−1 at best, which corresponds to a 40-year restoration period. In conclusion, we can say that in regions where agricultural production is very intense, carbon sequestration in the cropland may make only a very modest contribution to a country's effort to reduce greenhouse gas emissions.

We have studied the short term C mineralization of six wastes from important food industries, one sludge from a biogas plant and three composts. All the wastes were characterized chemically and fractionated according to the Van Soest method. The fresh wastes were incubated under controlled environment conditions to determine the C mineralization rate. Based on first order mineralization kinetics, we calculated the hypothetical amount of stable C in the wastes as the amount of C that would not be mineralized within one year under field conditions. The percentage of stable organic C in the organic matter was in general much larger in the composts than in the other wastes, but when expressed on dry matter, the non-composted wastes had comparable or larger amounts of stable organic C than the composts and have a considerable potential for supplying organic matter to soils, and hence for C sequestration. The amount of stable organic C could best be predicted by the total N content of the wastes (Ra2 = 0.855), whereas the results of the fractionation had very little predictive power, probably due to problems related to the high ash content of some of the wastes. An index that combined stable organic C and N and P content in the wastes was calculated to assess possible limitations for applying these wastes in agriculture. Under current nutrient legislation in Western Europe, a number of these wastes will only be usable in small amounts, but these and other food industry wastes could still prove to be valuable soil amendments in nutrient poor situations, for increasing soil organic C content and supplying nutrients.

In Western Europe, agriculture is one of the major contributors to the pollution of ground- and surface waters. Environmental concern has created the need for protection of these waters against eutrophication, caused by nutrient losses from e.g. agricultural sources. Leaching models may be used to predict nitrate-N losses to the environment and a plethora of such leaching models already exist. Four nitrate leaching models (Burns model, SLIM, SACFARM and ANIMO), with varying degree of complexity and parameter requirements, were used to simulate leaching in a bare fallow soil on a number of fields in the Wijlegem catchment in Flanders, Belgium. The models' performance was evaluated both statistically and graphically. Although all models predicted nitrate content in the soil profile within acceptable limits, the slightly adjusted Burns model appeared to simulate both the nitrate nitrogen and the water content best for the calibration field. Similar results were obtained for the evaluation field experiments: the Burns–α model simulated the moisture and nitrate content fairly well, while SLIM performed well in simulating the nitrate content. In conditions with limited data availability, simple (management) models, needing only a limited number of parameters to be measured or calibrated, may yield better simulation results than complex mechanistic models.

Trees play an important role in the biogeochemical cycling of metals, although the influence of different tree species on the mobilization of metals is not yet clear. This study examined effects of six tree species on fluxes of Cd, Zn, DOC, H(+) and base cations in forest floor leachates on a metal polluted site in Belgium. Forest floor leachates were sampled with zero-tension lysimeters in a 12-year-old post-agricultural forest on a sandy soil. The tree species included were silver birch (Betula pendula), oak (Quercus robur and Q. petraea), black locust (Robinia pseudoacacia), aspen (Populus tremula), Scots pine (Pinus sylvestris) and Douglas fir (Pseudotsuga menziesii). We show that total Cd fluxes in forest floor leachate under aspen were slightly higher than those in the other species' leachates, yet the relative differences between the species were considerably smaller when looking at dissolved Cd fluxes. The latter was probably caused by extremely low H(+) amounts leaching from aspen's forest floor. No tree species effect was found for Zn leachate fluxes. We expected higher metal leachate fluxes under aspen as its leaf litter was significantly contaminated with Cd and Zn. We propose that the low amounts of Cd and Zn leaching under aspen's forest floor were possibly caused by high activity of soil biota, for example burrowing earthworms. Furthermore, our results reveal that Scots pine and oak were characterized by high H(+) and DOC fluxes as well as low base cation fluxes in their forest floor leachates, implying that those species might enhance metal mobilization in the soil profile and thus bear a potential risk for belowground metal dispersion.

Acidification of forest soils in Europe and North America has been an important concern over the last decades. The last area-covering survey of forest soil acidification in Flanders (North Belgium) goes back to 1985 [Ronse A, De Temmerman L, Guns M, De Borger R. Evolution of acidity, organic matter content, and CEC in uncultivated soils of North Belgium during the past 25 years. Soil Sci; 146, (1988), 453-460] and highlighted a significant acidification of the upper layer (0.3-0.4 m) of forested podzols during the period 1950-1985. The present study aimed to assess (1) to what extent further acidification of forested podzols occurred during the period 1985-2000 at different depths and (2) whether the average annual acidification rate accelerated or slowed down between 1985 and 2000 compared to the period 1950-1985. Average soil pH-KCl values of podzols in northern Belgium dropped during the period 1985-2000. This decline extends to a depth of about 50 cm but was most pronounced and significant in the A horizon. In the A0, A1 and A2 horizons, average pH dropped with 0.2, 0.3 and 0.1 units, and in the Bir and C horizons with 0.1 units. No change in average pH value occurred in the Bh horizon. Average annual acidification rate of the A1 horizon was significantly higher in the period 1985-2000 than in the period 1950-1985. Changes in pH occurred in the entire soil profile during the period 1950/67-1985 likely because sulphate was the major form of acid deposition before 1985. After 1985, acid sulphur deposition decreased with more than 50% in North Belgium. In contrast, ammonium deposition almost doubled between 1950 and 1980, which may explain why soil acidification between 1985 and 2000 has been restricted to the upper soil horizons.

Intensive vegetable production systems throughout South East Asia are characterised by large nutrient inputs and low nitrogen (N) use efficiencies. In Indonesia, intensive vegetable production is concentrated on volcanic highland soils starting from an altitude of around 700 m above sea level. We measured potential N mineralisation from soil organic matter and from several representative organic materials in Andisols and Inceptisols with andic properties from Central Java, Indonesia. Unamended soils and soils amended with crop residues, animal manures, and compost were incubated during 3–4 months at 25°C in the laboratory, then we monitored N mineralisation. Relative N mineralisation was significantly smaller in the Andisols (average 3.6 ± 1.0%) than the Inceptisols (7.4 ± 2.9%), and was negatively related to oxalate-extractable aluminium (Alox) (r = –0.749) and soil organic carbon (r = –0.705). This is probably due to the strong protection of organic matter (and organic N) by binding to active Al compounds. Net N mineralisation from the added organic materials was highly variable (ranging from 68.1% for the broccoli residues to 2.6% for tithonia compost), and was best related to the organic N content (r = 0.476). There were no significant correlations between net N mineralisation and biochemical fractions, which we attribute to the large variety of materials used in this study compared with previous studies. The data generated here on N mineralisation potential from soil organic matter, and from a variety of plant materials and animal manures that are commonly used in these intensive vegetable rotations, will allow for the rapid and efficient introduction of N fertiliser advice systems based on balance sheets.

One of the most important problems in the Loess Plateau of China affecting sustainable agriculture is inefficient nutrient use. Field experiments were conducted to study the effects of different soil management practices on the nitrogen (N) dynamics and winter wheat yield on a loess soil in Luoyang, Henan province, China. The results showed that subsoiling with mulch (SS) consistently increased the yield of winter wheat primarily by better water harvest compared with conventional tillage (CT). The influence on yield of no till with mulch (NT) depended on the amount of precipitation. TC (2 crops per year) lowered the winter wheat yield mainly due to the unfavourable soil moisture conditions after growing peanut in summer; however, the harvested peanut gained an extra profit for the local farmer. N uptake by grain and straw and N export was highest for SS. Changes in frequency and intensity of tillage practice altered soil total N content and its distribution along the slope. SS and NT increased the N content of the surface layer (0–0.20 m) compared with CT, but there was no significant effect in deeper soil layers. Considerable amounts of nitrate-N were left in the profile 0–1.60 cm just after harvest under all treatments. The cumulative nitrate-N content to a depth of 1.60 m on average was 282 kg/ha, of which 56 kg/ha was in the layer 1.20–1.60 m, which is an indication of considerable nitrate leaching. From data of 7 consecutive years between 1999 and 2006, it could be concluded that SS resulted in the highest yield and total N content in the surface layer, and is the most sustainable tillage option for the circumstances of the study area.